It has been conventional in the field of video games and virtual reality to generate a view of a three-dimensional virtual space for display on a client terminal such as a smartphone and a game console. Ordinarily, a virtual space contains various objects including objects of a player character. A virtual space is generated based on various parameters such as parameters related to visual representation of the objects, parameters related to visual representation of a field or ground on which the objects are arranged, and parameters related to display position of the objects in the field.
A view of a virtual space is a visual representation of the virtual space as viewed from a virtual viewpoint (also referred to as “a virtual camera”) in the virtual space toward a fixation point. A user can interact with the virtual space through a view of the virtual space displayed on the display device. For example, a user can operate a user character in the virtual space to generate an event in the virtual space.
The view of the virtual space changes at any time in accordance with the movement of the viewpoint. For example, in some video games (e.g., first person shooting games), the viewpoint moves to follow the movement of a player character in the virtual space, and views corresponding to the positions of the viewpoint are generated. In video games having a virtual space containing a plurality of objects (e.g., strategic simulation games), the viewpoint moves sequentially to the positions of the objects generating events (movement, attack, use of an item, etc.) to display the events generated by the objects; and views corresponding to the positions of the viewpoint are generated.
However, when the viewpoint follows an object moving fast or when a plurality of objects generate events within a short time, the display screen changes fast or frequently in accordance with the position of the viewpoint and users watching the view sometimes feel uncomfortable. Such uncomfortable feeling is also called camera sickness. Since camera sickness may reduce the satisfaction of users, it is required to improve the control of how a viewpoint moves in a virtual space.
To relieve the camera sickness, Japanese Patent Application Publication No. 2008-212208 (Patent Literature 1) proposes that time and speed for a viewpoint to move in parallel is limited and, when the limit is exceeded, the parallel movement is cut short.